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Climate change may have one more side effect — another pandemic

AYESHA RASCOE, HOST:

In the next half century, climate change will create many more opportunities for viruses to leap between mammal species. That's according to a new study published Thursday in the journal Nature. And the increased risk of viruses transmitting across species means a higher risk of one that infects humans or even sparks another pandemic. Here to tell us more is Colin Carlson, a biologist at Georgetown University who's one of the study's authors. Welcome.

COLIN CARLSON: Thanks so much. Thanks for having me.

RASCOE: Can you start by explaining the link between climate change and viruses hopping between species? Like, how does one affect the other?

CARLSON: Sure. So the way I like to think of this - right? - is climate change is kind of going into ecosystems and shuffling the deck, right? We're used to ecosystems looking a certain way. But species have to move to sort of safer habitats. They have to move to cooler places to keep up with climate change. And when they do that, they're going to make new friends. They're going to meet new kinds of animals they've never met before. And that is bad news when it comes to viruses because it gives viruses a chance to jump into new hosts.

RASCOE: And you and your colleagues built a computer model to project how viral jumps between species might change in a warming world. What type of information did you use to build that model, and what did your results show?

CARLSON: So we've been running simulations on and off for about three years. We take huge climate models. We project where animals can go to track their habitats, and then we use machine learning to figure out what animals might be able to share viruses with each other. What we find is that everybody's on the move. We found that most species are probably going to have at least one chance to pick up new viruses. And at a sort of global scale, this is really concerning news when it comes to human health because it means that species like bats that have coronaviruses, Ebola virus, all of these things we worry about, they're probably going to need to share some of the same places that we already live. And they're going to be sharing a ton of viruses in our backyard.

RASCOE: One of the theories about how COVID started is that it started in an animal source. And scientists have identified hundreds of other human diseases that started in animals. Can you talk more about those implications of your findings for how this could affect people and, you know, maybe even cause another pandemic?

CARLSON: So it's pretty bad news for people. When viruses move from one species to the next, it's easier to do that if those species are more similar. It's hard to do big jumps across the tree of life. And what we are looking at here essentially is a global situation where a bunch of viruses that have evolved in bats may have the opportunity to jump into primates, to jump into cats and dogs - all of the things that might make it easier for them to eventually reach us because the jump might be a little bit less far next time. And so we think that there is a very high risk that these kinds of changes will at least spark more outbreaks. Now, whether those become pandemics, that's a choice, right? We have the ability to keep disease spillover from becoming pandemics. But we didn't do it this time, and there continues to be a risk we won't do it next time.

RASCOE: You can't really say exactly what will happen because you can't predict the future. You're just saying bringing all of these factors together is a risk.

CARLSON: I think that's exactly right. The way I like to think of it is there's parts of the future we can predict and parts that we can't. Viruses are the wildcard in all of this. We don't know which virus will spill over. We definitely don't know when viruses will make the jump. But we know what the momentum is in the system. And we have the opportunity right now in this moment to look at that momentum and do something about it before all of those thousands or millions of possibilities collapse down into one very bad reality, right?

We can try to collect more data and better understand how ecosystems are changing and where viruses are showing up. We can build better health systems and try to prevent outbreaks from becoming pandemics. And then we need to hold fossil fuel companies accountable for that. What we are talking about is a global change in the risk calculus of pandemics, and that comes from the fact we have waited decades to fade out fossil fuels. So I think there has never been a better moment to act for people's health, to act for climate, to really do something about all of this.

RASCOE: That's Colin Carlson, biologist at Georgetown University. Thank you so much.

CARLSON: Thanks for having me. Transcript provided by NPR, Copyright NPR.

Ayesha Rascoe is a White House correspondent for NPR. She is currently covering her third presidential administration. Rascoe's White House coverage has included a number of high profile foreign trips, including President Trump's 2019 summit with North Korean leader Kim Jong Un in Hanoi, Vietnam, and President Obama's final NATO summit in Warsaw, Poland in 2016. As a part of the White House team, she's also a regular on the NPR Politics Podcast.